Devices for harvesting vibration energy are often mechanical resonators with high-Q, wherein Q is the quality factor of the resonator. One example of such a device is a piezoelectric harvester. The piezoelectric harvesting devices typically have a cantilever that vibrates when it is in the presence of vibration energy. The cantilever is coupled to or otherwise connected to piezoelectric material that generates electricity from the vibrations.
One problem with high-Q mechanical resonators, such as piezoelectric harvesters, is that they resonate at a single frequency, whereas the sources of vibration energy are usually not monotonic, stable, and predictable. Therefore, there is a mismatch between the mechanical resonant frequency of the piezoelectric harvesters and the frequency of the vibration sources. The result is low power output from the mechanical resonators.